Not infrequently, a problem arises in connection with attempts at anchoring towers, large machine tools and other structures in concrete footings or slabs. Conventional practice is to bore a cylindrical hole, place the item to be anchored in the hole thus formed and pour fresh concrete back into the hole to form the anchor. Unfortunately, such anchors rely primarily on the weight of the anchor and whatever bond can be established between the anchor and the cylinder wall. Some shrinkage in the size of the anchor is bound to take place which further lessens its ability to adhere to the adjacent bore wall. A much better anchor could be made if the wall of the bore could be grooved circumferentially such that ribs of wet concrete would form around the plug which, once set, would hold it in place.
While the prior art is replete with reamers, boring tools, groove cutters and the like which are used for such things as cutting off pipe downhole, smoothing the sides of machined surfaces, honing away ribs at the top of a cylinder in the block of an internal combustion engine and other similar applications, these tools are ill-suited to the task of reaming grooves in concrete bores. One of the main problems encountered in the latter application is the fact that not infrequently one encounters large voids in the bore wall which cause the ordinary groove-cutting tool to jam. Another factor is, of course, the hostile environment in which the tool works in terms of dust, grit, sand, abrasive cuttings, chunks of rock and whatever else might lie in the wall of the bore or just outside it.
1. Field of the Invention
The present invention relates, therefore, to rotary tools for cutting grooves in the walls of concrete bores.
2. Description of the Related Art
Probably the basic tool for use in cylindrical bores is the reamer or hone. Good examples of such tools are found in the U.S. Patents to Heon Nos. 1,550,807 and 1,774,711; Emerson No. 1,742,466 and Klumpp No. 2,778,167. Of a similar nature is the Solbrig U.S. Pat. No. 2,229,314 which instead of honing or otherwise dressing the entire bore, is designed for use as a ridge-removal tool when reboring internal combustion engine cylinders. These reamers are not at all suited for use in hostile environments like concrete bores nor do they cut grooves in the bore wall.
Next, one encounters a number of inside pipe cutters like, for example, the U.S. Patents to Braswell No. 3,283,405; Wright et al No. 3,739,666; Thompson No. 4,389,765 and Montiero No. 4,524,511. The cutter wheels and eccentrically-mounted cutter heads in these patents all appear to produce narrow saw-like cuts which are not suitable for grooving concrete bores to receive integrally-formed ribs bordering a cast-in-place concrete anchor or plug.
As one might expect, there are also groove cutters for cutting circumferential grooves in the walls of hollow cylindrical elements. While the under-reamer forming the subject matter of Johnson's U.S. Pat. No. 2,879,038 includes a pair of eccentrically-mounted cutters spring-biased into retracted position, nevertheless, these cutters are spaced apart circumferentially 180.degree. and, therefore, would "hang-up" in a void found in the bore wall. The cutters ih Berruyer et al's U.S. Pat. No. 3,389,620 are only spaced apart 120.degree. but they suffer from the same inability to bridge a gap without hanging up. Also, they move radially not on eccentric spring-biased "fly-away" mounts. The Ronaldson et al Pat. No. 2,966,766 is more of a reamer than it is a bore-groover and it, like the previously mentioned patent to Berruyer et al has its cutters spaced 120.degree. apart at their lines of tangency with the bore. The Kessler et al Pat. No. 4,444,279 is most certainly a bore-grooving tool, however, the way in which the cutters are moved radially out against the bore wall using a wedge principal is entirely different from that used by applicant.
From the above it can be seen that the basic concept of mounting the cutters on eccentrically-mounted flyweights which swing out against the bore wall is old in the art as is the use of springs to bring the flyweights back in again so that the tool can be removed. None of these tools, however, shows stacked overlapping cutter subassemblies that extend circumferentially around a substantial portion of the bore and, in addition, overlap one another in staggered relation such that at least one such cutter in each flyaway subassembly will be seated in its groove and be in position to prevent the one or more of the other cutters in the same subassembly from hanging up at the edge of a void. Moreover, these prior art patents are deficient in sealing the moving parts of the system from the abrasive action of the cuttings and the otherwise hostile environment in which the tool is used.